The Prophet ﷺ said: He who is asked something he knows and conceals it will have a bridle of fire put on him on the Day of Resurrection.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ سُئِلَ عَنْ عِلْمٍ فَكَتَمَهُ أَلْجَمَهُ اللَّهُ بِلِجَامٍ مِنْ نَارٍ يَوْمَ الْقِيَامَةِ